Hand operated tools for cutting tubing, light pipe, and other hollow cylindrical materials are well known, with such devices generally including a cutter blade or wheel disposed opposite a pair of rollers, thus providing triangulation and positive location around the circumference of the material being cut. The cutting device is rotated about the circumference of the material being cut, in order to move the cutting blade completely around the material.
One feature universal of all such cutting devices is a means to advance the cutting blade into the material being cut as the operation is performed, due to the ever increasing depth of the cut as the operation progresses. Quite obviously, if the cutting blade is not advanced, an initial shallow cut would be made about the circumference of the material and no further cutting action would take place. The general method for advancing the cutting blade in prior art implements is by means of a threaded screw advance of the rotary cutting blade. Although the positive advancement thereby provided is effective, it generally requires manual advancement of the cutting blade by means of the screw adjustment every one or two turns of the cutter around the material, which obviously is a tedious procedure if the material being cut has a relatively thick wall. Moreover, great care must be used in advancing the cutting blade inasmuch as the blade edge may be dulled or damaged, or more importantly, the sidewall of the tubing may be so badly deformed as to drastically impair the cutting procedure if the screw advance is tightened too much. On the other hand, too little force on the cutting blade advance means results in a relatively slow and inefficient cutting operation.
Additional features are desirable in such cutters to further enhance the cutting operation, such as a fine adjustment of a spring force utilized for biasing the cutting blade toward the rollers, in order to optimize the cutting rate and pressures.
The need arises for a cutting tool for tubing or the like that is capable of automatically providing constant pressure to the material being cut by the cutting blade or wheel. Such a tool makes it possible to obviate any requirement for manual adjustment of the tool during the cutting operation, with the constant pressure applied to the material being selectable by the user by reference to scales conveniently provided on the tool. Also needed is an override arrangement such that the pressure applied by the cutter wheel to the tubing can be directly controlled during the cutting of tubing that is particularly hard or difficult to cut.
It was in an effort to achieve these and other significant objectives that the present invention was made.